Image forming method and apparatus

Abstract

The image forming method forms an image on a medium by using ink and treatment liquid. The ink contains coloring material and thermoplastic resin particles in a solvent, and the treatment liquid contains a component which aggregates the coloring material. The image forming method includes: a treatment liquid deposition step of depositing the treatment liquid onto the medium to form a treatment liquid film on the medium; an ink droplet deposition step of ejecting and depositing droplets of the ink onto the medium to form an ink film on the medium on which the treatment liquid film has been formed; and an ink film drying step of heating and drying the ink film under conditions where T<MFT+20° C. until α declines to a state not higher than 2.0 from a state exceeding 2.0, where T is a surface temperature of the ink film, MFT is a minimum film forming temperature of the thermoplastic resin particles, and α is a solvent content rate of the ink film formed on the medium in the ink droplet deposition step defined as a volume of the solvent per unit surface area in the ink film divided by a volume of solid material per unit surface area in the ink film.

1. An image forming method of forming an image on a medium by using ink and treatment liquid, the ink containing coloring material and thermoplastic resin particles in a solvent, the treatment liquid containing a component which aggregates the coloring material, the method comprising:
 a treatment liquid deposition step of depositing the treatment liquid onto the medium to form a treatment liquid film on the medium; 
 an ink droplet deposition step of ejecting and depositing droplets of the ink onto the medium to form an ink film on the medium on which the treatment liquid film has been formed; and 
 an ink film drying step of heating and drying the ink film under conditions where T<MFT until α declines to a state not higher than 2.0 from a state exceeding 2.0, where T is a surface temperature of the ink film, MFT is a minimum film forming temperature of the thermoplastic resin particles, and α is a solvent content rate of the ink film formed on the medium in the ink droplet deposition step defined as a volume of the solvent per unit surface area in the ink film divided by a volume of solid material per unit surface area in the ink film. 
 
     
     
       2. The image forming method as defined in  claim 1 , further comprising a treatment liquid film drying step of heating and drying the treatment liquid film on the medium formed in the treatment liquid deposition step, after carrying out the treatment liquid deposition step and before carrying out the ink droplet deposition step. 
     
     
       3. The image forming method as defined in  claim 1 , wherein, in the ink film drying step, the heating and drying are carried out by setting the film surface temperature T to be not lower than MFT by a time of completion of the heating and drying of the ink film after the solvent content rate α has become not higher than 2.0. 
     
     
       4. The image forming method as defined in  claim 1 , wherein, in the ink film drying step, the heating and drying are carried out by raising the film surface temperature T after the solvent content rate α has become not higher than 2.0. 
     
     
       5. The image forming method as defined in  claim 1 , further comprising a fixing step of pressing and fixing the ink film onto the medium by means of a heated member, after carrying out the ink film drying step. 
     
     
       6. An image forming apparatus which forms an image on a medium by using ink and treatment liquid, the ink containing coloring material and thermoplastic resin particles in a solvent, the treatment liquid containing a component which aggregates the coloring material, the apparatus comprising:
 a treatment liquid deposition device which deposits the treatment liquid onto the medium to form a treatment liquid film on the medium; 
 an ink droplet ejection device which ejects and deposits droplets of the ink onto the medium to form an ink film on the medium on which the treatment liquid film has been formed; and 
 an ink film drying device which heats and dries the ink film under conditions where T<MFT until α declines to a state not higher than 2.0 from a state exceeding 2.0, where T is a surface temperature of the ink film, MFT is a minimum film forming temperature of the thermoplastic resin particles, and α is a solvent content rate of the ink film formed on the medium by the ink droplet deposition device defined as a volume of the solvent per unit surface area in the ink film divided by a volume of solid material per unit surface area in the ink film.